This proposed research project is concerned with the morphological and physiological features of the lymphatic capillaries and the role of this system under normal physiological conditions, as well as during the inflammatory response. A detailed ultrastructural investigation of the lymphatic capillaries is being undertaken in an effort to provide information that will further our understanding of the topographic relation of the lymphatic vascular system to the surrounding connective tissue area and the blood vascular system. The removal of interstitial fluids by the lymphatic capillaries is being investigated by following the progress of vital dyes and colloidal substances after interstitial injections. The development and growth of lymphatics are being studied using the rabbit ear chamber technique. This technique also allows one to inject bacteria as well as chemicals so that observations can be made on a controlled living system. These ultrastructural and physiological studies on the lymphatic system will provide information that will further our understanding of the processes involved in the transfer of interstitial fluids from the connective tissue area into the lymphatic capillaries during both normal and inflamed conditions. BIBLIOGRAPHIC REFERENCES: Leak, Lee V.: Cytoarchitecture of the definitive bursa of the Fabricius, Anatomical Record 181:407, 1975. Leak, Lee V. and K.S. Rahil: Topographical relationship of diaphragmatic lymphatics to the pleural and peritoneal surfaces. J. Cell Biol. 67, 236, 1975.